Optical Instruments Questions and Answers

Q44 A coherent parallel beam of microwaves of wave length 0 5 mm falls on a Young s double slit appa ratus The separation between the slits is 1 0 mm The intensity of microwaves is measured on a screen placed parallel to the plane of the slits at a distance of 1 0 m from it as shown in the figure 1998 30 d 1mm D 1 0m Y a If the incident beam falls normally on the double slit apparatus find the y coordinates of all the in terference minima on the screen b If the incident beam makes an angle of 30 with the x axis as in the dotted arrow shown in figure find the y coordinates of the first minima on either side of the central maximum

An object and a screen are mounted on an optical bench and a converging lens is placed between them so that a sharp image is obtained on the screen The linear magnification of the image is 25 The lens is now moved 30 cm towards the screen and a sharp image is again formed on the screen Find the focal length of the lens A 1 2 cm C 14 6 cm B 14 3 cm D 14 9 cm

A transparent solid sphere of radius 2 cm and density p floats in a transparent liquid of density 2p kept in a beaker The bottom of the beaker is spherical in shape with radius of curvature 8 cm and is silvered to make it concave mirror as shown in the figure When an object is placed at a distance of 10 cm directly above the centre of the sphere its final image coincides with it Find h as shown in the figure the height of the liquid surface in the beaker from the apex of the bottom Consider the paraxial rays only The refractive index of the sphere is 3 2 and that of the liquid 4 3

An electron in the ground state of hydrogen atom is revolving in anticlock wise direction in a circular orbit of radius R 1996 5 Marks Obtain an expression for the orbital magnetic dipole moment of the electron Bi

A graded index fiber has a core diameter of 0 25 mm and a numerical aperture of 0 22 at a wavelength of 8000 Find the normalised frequency mention the value to the nearest second decimal

A convex lens of focal length 24 cm refractive index 1 50 is totally immersed in water 2 marks refractive index 1 33 Find its focal length in water

tion is c 4f 3 b 2 a f d 3f 0 A convex lens of focal length 15 cm is placed e plane mirror An object is placed at 30 cm from the lens The image is a real at 30 cm in front of the mirror b real at 30 cm behind the mirror c real at 10 cm in front of the mirror d virtual at 10 cm behind the mirror In the given figure the

If we want to observe diffraction pattern of a wave then size of obstacle should be O Very large as compare to wavelength of wave O Very small as compare to wavelength of wave O Nearly equal to wavelength of wave O of any size

c 18 cm 2 cm For the angle of minimum deviation of a prism to be equal to its refracting angle the prism must be made of a material whose refractive index a lies between 2 and 1 2012M b lies between 2 and 2 c is less than 1 d is greater than 2

22 In a setup of displacement method experiment distance between the screen and a light source is 120 cm and the lens used has a small aperture By moving the lens between the source and the screen sharp images are obtained on the screen for two different positions of the lens The ratio of sizes of these two images is 1 9 a What is the focal length of the lens b Which image is the brighter one Determine the ratio of the brightness of these two images This one is to be served

The energy band diagrams for three semiconductor samples of silicon are as shown We can then assert that 1 Sample X is undoped while samples Y and Z have been doped with a third group and a fifth group impurity respectively 2 Sample X is undoped while both samples Y and Z have been doped with a fifth group impurity 3 Sample X have been doped with equal amounts of third and fifth group impurities while samples Y and Z are undoped 4 Sample X is undoped while samples Y and Z have been doped with a fifth group and a third group impurity respectively

A fly is sitting on objective of a telescope pointed towards moon What effect is expected in the photograph of the moon taken through telescope O There is an image of fly on photograph The entire field of view is blocked There is reduction in intensity of image

In the situation shown the incident monochromatic ray retraces its path after its incidence on the silvered surface The speed of light inside the prism will be ncident ray 30 30 3 x 108 ms 1 2 x 108 ms 1 1 41 x 108 ms7 1 73 x 108 ms 1 Silvered

Two plane mirrors M1 ans M2 each have length 2 m and are separated from one another by 1 cm A ray of light is incident on one end of mirror M1 at angle 45 How many reflections the ray will suffer on mirror M2 before going out from the other end 100 200 101 201 My M

Question No 13 Two wires of same material and length are stretched by same force Their masses are in ratio 1 3 their elonga O 1 2 O 4 1 O 3 1 O 4 5

An object is placed 15 cm infront of a concave mirror whose focal length is 10 cm The image formed will be magnified and inverted magnified and erect reduced in size and inverted reduced in size and erect

If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm the focal length of the eye piece should be close to 2 12 mm 1 22 mm 3 33 mm 4 2 mm

A new space telescope is built and successfully launched to orbit to search for planets outside of our solar system The diameter of the telescope s main mirror is 36 9 cm The telescope s camera is designed to work best in the near infrared range at a wavelength of 999 0 nm What is the angular resolution of the telescope Hint use the Rayleigh criterion for circular apertures

A light ray traveling in glass medium is incident on glass air interface at an angle of cidence 8 The reflected R and transmitted T intensities both as function of 0 are plotted The correct sketch is A ti ti 100 T C 100 Intensity 100 Intensity T 90 90 B D Intensity Intensity 0 90 90

A ray of light strikes a transparent surface from air at an angle 0 If the angle between the reflected and refracted ray is a right angle the refractive index of the other surface is given by B u tan 0 D tan 0 A tan 0 C sin 0

er In an astronomical telescope the focal length of the objective lens is 100 cm and of eye piece is 2 cm The magnifying power of the telescope for the normal eye is 1 50 2 10 3 100 4 70 50

An inverting amplifier is to be constructed having a mid band voltage gain of 40 an input resistance of 5 kQ and a frequency response extending from 20 Hz to 20 kHz Devise a circuit and specify all component values required

diveLance i Objective lens forms real magnified and inverted image ii Eye piece lens forms real inverted and diminished image iii The magnifying power of eyepiece is same as that of simple microscope iv The final image is never inverted with respect to the original object SolveLancer Test a i only b ii and iv c i and iii d iv only

Q 31 Moderate O 0 4 1 00 30 A ray of light is incident on a plane mirror at an angle 57 The resultant 90 O polarized light vibrates in a plane which makes an angle with the reflecting surface 000

through a converging lens of A stationary observer looking at a fish F in water of focal length 90 0 cm The lens is allowed to fall freely from a height 62 0 cm with its axis vertica The fish and the observer are on the principal axis of the lens The fish moves up with constant velocity 100 cm s Initially it was at a depth of 44 0 cm if the velocity with which the fish appears to move to the observer at t 0 2 sec is g 10 m s A B C 91 4 95 4 99 4 ms 1 ms 1 ms 1 Lens water 62 cm 44 cm

object O and its image is 24 cm The object is 6 cm above water level and the beaker containing water upto 8 cm is kept on a plane mirror Refractive index of the water is 1 N W 2 L Water 6 cm 43 7 8 cm Mirror

18 In the following circuit the emf of source is E 200 volt R 20 92 L 0 1 henry C 10 6 farad and frequency is variable then the current at frequency f 0 and f is 1 Zero 10 A 2 10 A zero 3 10 A 10 A 4 Zero zero

Q 27 erate 4 1 00 30 The position of final image formed by the given lens combination from the third lens will be at a distance of f 10 cm f 10 cm f 30 cm or

Draw a ray diagram showing the image formation of a distant object by a refracting telescope Define its magnifying power and write the two important factors considerec to increase the magnifying power Describe briefly the two main limitations and explain how far these can be minimized in a reflecting telescope

D Two concave mirror of focal length f and f2 are placed facing each other and d distance apart Find the value of dmin If object is between the mirrors that object and image will coincide f f 2f 2f f 2f Maximum Mark 4 00 2f f ENG

SolveLancer Test Given R m m s s e e m e s e s m e m is relation on set A m e s i then relation R is SolveLancer Test a reflexive only b transitive only c reflexive symmetric but not transitive d reflexive transitive but not symmetric

L Q 11 Moderate O 64 127 O 4 3 O In a given direction the intensities of the scattered light by a scattering substance for two beams of light are in the ratio of 256 81 The ratio of the frequency of the 1 first beam to the frequency of the second beam is 64 27 00 19 O

Q3 An object is moving towards a stationary plane mirror with a speed of 2 m s in left Velocity of the image w r t the object is a 2 m s towards right JIO b 4 m s towards right c 2 m s towards left d 4 m s towards left

40 45 Multiple Choice Select 1 out of 4 options for the question below 50 An image formed by a convex mirror is always 55 59 60 Options virtual erect and diminished O virtual real and magnified Oreal inverted and diminished Oreal erect and magnified Clear Response

If the speed of light C acceleration due to gravity g and pressure p are taken as the fundamental quantities then the dimensions of length will be A c g p B cg p C c gp D cg p A

A rod of length 30 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror The length of the image is CBSE AIPMT 2012 B 15 cm D 5 cm A 10 cm C 2 5 cm

Two tuning forks have frequencies 380 and 384 Hz respectively When they are sounded together they produce 4 beats After hearing the maximum sound how long will it take to hear the minimum sound Option A B C 18 sec sec sec Rate this quest

In the figure is shown Young s double slit experiment Q is the position of the first bright fringe on the right side of O P is the 11th fringe on the other side as measured from Q If the wavelength of the light used is 6000 10 10 m then S B will be equal to S Slit B P

A cylindrical optical fibre quarter circular shape of refractive index n 2 and diameter d 4mm is surrounded by air A light beam is sent into the fibre along its axis as shown in figure Then the smallest outer radius R in mm as shown in figure for which no light escapes after first incident on curved surface of fibre is

39 A vessel having perfectly reflecting plane bottom is ann was filled with water to a depth d A point source of light is placed at a height h above the surface of water The distance of final image from water surface is 1 h d 3 3 h d 4 924 S 3 2 h 2 3 4 h d

Two sound sources of same frequency are placed at distance of 100 meter An observer when moving between both sources hears 4 beats per second The distance between sound source is now changed to 400 meter then the beats second heard by observer will be A B C 2 4 8

An object and a concave mirror of focal length 20 cm approach each other with a speed of 1 cm s and 2 cm sec respectively At the instant when the object is at a distance of 15 cm from the mirror the speed of image is 1 50 cm sec 3 16 cm sec 2 18 cm sec 4 8 cm sec

A Plano convex lens u 1 5 of focal length 20 cm Now its plane side is silvered Which of the Collowing statements is are correct A The radius of curvature of its curved surface is half that of a surface of equiconvexlens of focal length 20 cm made of same material B An object placed at 15 cm on the axis on the convex side of silvered plano convex lens gives rise to an image at a distance of 30 cm from the surface C An object placed at a distance of 20 cm on the axis on the convex side of silvered plano convex lens gives rise in an image at 40 cm from the surface R It acts as a convey mirror

3 The object is at a distance of 45 cm from the screen With the help of lens we obtain a small image of the object on the screen By moving the lens we receive a different image on the screen whose size is 4 times greater than the first What is the focal length in cm of the lens

The Vernier scale of an instrument has 50 divisions which coincide with 48 main scale division If each main scale division is 1 mm then using this instrument the inaccuracy in the measurement of distance is 0 04 mm 0 4 nm 0 004 mm 4 cm

In accordance with Kirchhoff s law for a black body radiation which one is wrong Bad absorber is a bad emitter Bad reflector is a good emitter Bad emitter is a good absorber

Example 9 11 a The far point of a myopic person is 80 cm in front of the eye What is the power of the lens required to enable him to see very distant objects clearly b In what way does the corrective lens help the above person Does the lens magnify very distant objects Explain carefully c The above person prefers to remove his spectacles while reading a book Explain why

dence the person prefers to remove the spectacles Example 9 12 a The near point of a hypermetropic person is 75 cm from the eye What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye b In what way does the corrective lens help the above person Does the lens magnify objects held near the eye c The above person prefers to remove the spectacles while looking at the sky Explain why ne th

or hypermetropia Example 9 10 What focal length should the reading spectacles for a person for whom the least distance of distinct vision is 50

Half part of the rear surface of a thin equiconvex lens of focal length 40 cm and refractive index 1 5 is silvered If parallel rays are incident on this lens then the distance between the two focii is